This invention relates to the field of elevator and escalator control, and in particular, to the use of an integrated shaft sensor for load measurement and torque control.
In an elevator system, one reason loadweighing is done is so that the elevator motor/machine can apply some torque before it lifts the brake that is holding an elevator car stationary at a floor where it is stopped. If the right amount of torque is applied based on the load, i.e., the number of people in the car, then the car remains motionless at the floor when the brake is lifted. If the correct amount of torque is not applied, the car lifts up or drops down a bit when the brake is lifted and before the motion control system takes control of operations. That lift up or drop down is known as rollback, and passengers do not like it at all. Other uses for loadweighing information include improved motion control of the car and making operating decisions such as, for example, anti-nuisance, overload, etc.
Loadweighing is conventionally done with sensors under the elevator car floor, but they are difficult to install, adjust, and maintain, and of course involve the added burden of putting in wires for the sensors, bringing the signals from the car up to the control system, etc. Platform systems suffer from inaccuracies due to friction in floor movement or imperfect distribution of the load.
Another way to do loadweighing is to put a sensor in the hitch, i.e., the place where the steel cables attach to the car. Hitch cells require top of car access for installation and service, and suffer inaccuracies from measuring small weight changes to the total car weight. Machine beam sensor systems have similar problems. This make the small change on top of a large weight problem worse, as the counterweight is now also being weighed.
Briefly stated, an elevator machine and control system includes a drive shaft with a motor and brake. A rope, usually a steel cable or belt, is attached at one end to an elevator car and at the other end to a counterweight. The rope is reeved around a traction sheave connected to the drive shaft. At least one torque sensor is integrated into the machine""s drive shaft between the brake and the traction sheave. A controller operates the motor based in part upon a feedback signal received from the torque sensor. Depending on the location of the brake vis a vis the motor and traction sheave, either one sensor or two sensors are required to produce a feedback signal which is indicative of a load in the elevator car.
According to an embodiment of the invention, an elevator machine and control system includes a drive shaft; a motor operatively connected to the drive shaft, wherein the motor turns the drive shaft; a brake operatively connected to the drive shaft, wherein the brake stops the drive shaft from turning; a traction sheave operatively connected to the drive shaft, wherein turning the drive shaft turns the traction sheave; a rope reeved over the traction sheave; at least one torque sensor integrated into the drive shaft; and a controller for controlling the motor, wherein the controller receives a feedback signal from the at least one torque sensor.
According to an embodiment of the invention, an elevator machine and control system includes a drive shaft; a motor operatively connected to the drive shaft, wherein the motor turns the drive shaft; a brake operatively connected to the drive shaft, wherein the brake stops the drive shaft from turning; a traction sheave operatively connected to the drive shaft, wherein turning the drive shaft turns the traction sheave; a rope reeved over the traction sheave; wherein the rope is connected to an elevator car and a counterweight; at least one torque sensor integrated into the drive shaft between the brake and the traction sheave; and a controller for controlling the motor, wherein the controller receives a feedback signal from the at least one torque sensor.